Ink jet recording process

ABSTRACT

Recording onto a non-ink-absorbing recording medium is performed using an aqueous ink composition containing a first solvent composed of at least one selected from 2-pyrrolidone, 1,3-dimethyl-imidazolidinone, and N,N′-dimethylpropylene urea, a second solvent composed of at least one selected from 1,2-hexanediol and 1,2-pentanediol, and a third solvent composed of at least one selected from glycol diethers and heating the non-ink-absorbing recording medium at 40 to 60° C.

BACKGROUND

1. Technical Field

The present invention relates to a recording process using an aqueousink for performing ink jet recording on a recording medium having anon-ink-absorbing recording surface, such as plastics.

2. Related Art

In known methods for recording on non-ink-absorbing recording media,non-aqueous inks containing main components of organic solvents havebeen widely used. For example, as a non-aqueous ink jet ink for printinghigh-quality images and characters on a surface of a vinylchloride-based resin material, such as a polyvinyl chloride sheet, whichis widely used as a medium, for example, for outdoor advertisements,inks each containing a pigment excellent in light resistance, a resincomponent for fixing the pigment to the surface of a vinylchloride-based resin material, and an organic solvent that can dissolvethe resin component are commonly used. These non-aqueous inks areexcellent in some aspects, for example, satisfactory water resistancecaused by using both a water-insoluble coloring agent and awater-insoluble resin component and prevention of images from bleedingdue to quick drying caused by using a highly volatile solvent. However,since an image is formed by volatilization of the solvent on the surfaceof a recording medium, there are problems of an odor and toxicity of thesolvent during drying. Furthermore, influences of organic solvents onthe environment have been concerned.

For example, JP-A-2007-291257 discloses an ink jet recording processusing an ink jet ink that is a non-aqueous ink jet ink containing arelatively high-safety organic solvent and being thereby excellent inprinting suitability to polyvinyl chloride (PVC), a kind ofnon-absorptive recording medium, emission stability, and safety and notcausing a problem of odor. However, the ink contains, as an example, amain solvent of diethylene glycol diethyl ether in not less than 80 mass%, and it is therefore obvious that the safety is significantly lowcompared to aqueous inks. In addition, influences of the large amount ofthe volatile solvent on the environment are considerable. Accordingly,there is a demand for a recording process using an aqueous ink inrecording on a non-ink-absorbing recording medium, such as a polyvinylchloride sheet, from the viewpoints of safety and protection of theenvironment.

Against this problem, for example, JP-A-2008-260820 discloses an aqueousheat fixing ink that is an aqueous ink jet ink, gives a satisfactoryhigh-speed printing image quality not causing defects such as spots on anon-absorptive recording medium, and can be stably used for a long timeand discloses a heat fixing ink jet recording process using the ink. Theamount of an organic solvent is 10 to 35 mass %, and diethylene glycoldiethyl ether is mentioned as an example of the organic solvent. It isdescribed that a combination of a specific organic solvent and awater-soluble resin and heating of the non-absorptive recording mediumto 40 to 90° C. inhibit spots from occurring to give satisfactoryrecording image quality.

On the other hand, polyvinyl chloride causes defects, such asdeformation and dimensional change due to expansion and contraction, ata temperature higher than 60° C. However, JP-A-2008-260820 does notmention abrasion resistance in heating printing at a temperature rangeof 40 to 60° C. in which polyvinyl chloride can be prevented fromsoftening. Thus, in recording using an aqueous ink on a polyvinylchloride material, an effective ink jet recording process showingabrasion resistance that is equal to that of a non-aqueous ink has notbeen established yet.

SUMMARY

An advantage of some aspects of the invention is to provide an ink jetrecording process achieving recording on a recording medium having anon-absorptive recording surface, in particular, a recording mediumcomposed of polyvinyl chloride to form an image having high-quality andabrasion resistance due to an excellent quick-drying property and lessbleeding of the ink by performing the recording while heating therecording medium at a temperature range of 40 to 60° C. at whichpolyvinyl chloride can be heated without causing problems.

An advantage of some aspects of the invention is to solve at least apart of the problems described above, and the invention can be realizedas the following aspects or application examples.

Application Example 1

An aspect of the ink jet recording process according to the inventionincludes a first step of heating a recording medium of a polyvinylchloride film to a temperature range of 40 to 60° C. and dischargingdroplets of an aqueous ink composition with an ink jet recordingapparatus; and a second step of heating the recording medium to atemperature range of 40 to 60° C. to dry the aqueous ink compositiondischarged on the recording medium, wherein

the aqueous ink composition contains water, at least one kind ofwater-insoluble coloring agent, water-insoluble thermoplastic resinparticles, a surfactant, a first solvent composed of at least oneselected from 2-pyrrolidone, 1,3-dimethyl-imidazolidinone, andN,N′-dimethylpropylene urea, a second solvent composed of at least oneselected from 1,2-hexanediol and 1,2-pentanediol, and a third solventcomposed of at least one selected from glycol diethers having a boilingpoint of 150 to 220° C., wherein

the content (W1) of the first solvent in the aqueous ink composition is4 to 15 mass %, the content (W2) of the second solvent in the aqueousink composition is 3 to 8 mass %, the total content (W1+W2) of the firstsolvent and the second solvent is 18 mass % or less, and the content(W3) of the third solvent in the aqueous ink composition is 4 to 20 mass%.

According to the ink jet recording process of Application Example 1,recording being excellent in quick-drying property, reducing bleeding ofan image formed on a non-ink-absorbing recording medium, and providing arecorded matter excellent in abrasion resistance can be achieved.

Application Example 2

In the ink jet recording process according to the above-mentionedapplication example, the glycol diethers of the third solvent are atleast one selected from diethylene glycol dimethyl ether, diethyleneglycol diethyl ether, diethylene glycol ethyl methyl ether, diethyleneglycol butyl methyl ether, and triethylene glycol dimethyl ether.

Application Example 3

In the ink jet recording process according to the above-mentionedapplication examples, the water-insoluble coloring agent is a pigmentand is dispersed in the aqueous ink composition with a water-solubleresin.

Application Example 4

In the ink jet recording process according to the above-mentionedapplication examples, the water-insoluble thermoplastic resin particlesare made of an acrylic resin or a styrene-acrylic acid copolymer resin.

Application Example 5

In the ink jet recording process according to the above-mentionedapplication examples, the surfactant is a silicon-based surfactant.

Application Example 6

In the ink jet recording process according to the above-mentionedapplication examples, the heating of the recording medium is performedwith a heater or warm air.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Preferred embodiments of some aspects of the invention will be describedbelow. The embodiments described below are merely examples of theinvention. The invention is not limited to the following embodiments andincludes various modifications implemented within the scope of theinvention.

1. Ink Jet Recording Process

The ink jet recording process according to an embodiment of theinvention includes a first step of heating a recording medium of apolyvinyl chloride film, to a temperature range of 40 to 60° C. anddischarging droplets of an aqueous ink composition with an ink jetrecording apparatus; and a second step of heating the recording mediumto a temperature range of 40 to 60° C. to dry the aqueous inkcomposition discharged on the recording medium. The aqueous inkcomposition contains water, at least one kind of water-insolublecoloring agent, water-insoluble thermoplastic resin particles, asurfactant, a first solvent composed of at least one selected from2-pyrrolidone, 1,3-dimethyl-imidazolidinone, and N,N′-dimethylpropyleneurea, a second solvent composed of at least one selected from1,2-hexanediol and 1,2-pentanediol, and a third solvent composed of atleast one selected from glycol diethers having a boiling point of 150 to220° C. The content (W1) of the first solvent in the aqueous inkcomposition is 4 to 15 mass %, the content (W2) of the second solvent inthe aqueous ink composition is 3 to 8 mass %, the total content (W1+W2)of the first solvent and the second solvent is 18 mass % or less, andthe content (W3) of the third solvent in the aqueous ink composition is4 to 20 mass %. In the invention, the term “image” refers to a printedpattern formed by groups of dots and includes text patterns and solidpatterns.

1.1. Ink Jet Recording Process

The ink jet recording process according to a first embodiment of theinvention includes a first step of heating a recording medium of apolyvinyl chloride film to a temperature range of 40 to 60° C. anddischarging droplets of an aqueous ink composition with an ink jetrecording apparatus; and a second step of heating the recording mediumto a temperature range of 40 to 60° C. to dry the aqueous inkcomposition discharged on the recording medium.

The ink jet recording apparatus is not particularly limited as long asit can perform recording by discharging ink droplets and letting thedroplets adhere onto a recording medium, but preferably has a functionof heating a recording medium during printing. Herein, the term “duringprinting” refers to the period from the time immediately after that anink jet recording apparatus has discharged ink droplets and let thedroplets adhere onto a recording medium until the time when the ink hasbeen dried.

Examples of the function that can heat a recording medium include aprint heating function where a recording medium is brought into directcontact with a heat source and is heated, irradiation of a recordingmedium with infrared rays or microwaves (electromagnetic waves having amaximum wavelength at about 2450 MHz) without direct contact with therecording medium, and a dryer function where warm air is blown. Theprint heating function and the dryer function may be employed alone orsimultaneously. By this function, the drying temperature during printingcan be controlled.

Furthermore, ink droplets are discharged by the ink jet recordingapparatus, and the recording medium to which the droplets adhered may bedried with a dryer or in a thermostatic chamber that has been set to apredetermined temperature.

The recording process according to an aspect of the invention issuitable for printing on a recording medium made of polyvinyl chloride.Polyvinyl chloride recording media are commercially available as varioustypes of products for outdoor displays, which are required to haveweather resistance for a long time, and for application to be attachedto objects having curved surfaces. Any of these products can beappropriately selected according to application.

Furthermore, the recording process according to an aspect of the presentinvention can be applied to non-ink-absorbing or low-ink-absorbingrecording media, in addition to the recording media made of polyvinylchloride. Examples of non-ink-absorbing recording medium include plasticfilms not having aqueous ink-receiving layers, and base materials, suchas paper, provided with plastic coatings or plastic films thereon.Examples of the plastic film herein include those made of polyethyleneterephthalate, polystyrene, polyurethane, polyethylene, orpolypropylene. Examples of low-ink-absorbing recording medium includeprinting paper such as art paper, coated paper, and mat paper.

Here, in this specification, the phrase “non-ink-absorbing orlow-ink-absorbing recording medium” refers to a “recording medium thatabsorbs 10 mL/m² or less water from the initial contact with water untilwhen 30 msec1/2 has elapsed when measured by a Bristow method”. TheBristow method is most commonly used as a method for measuring theamount of liquid absorbed in a short period of time, and Japan TechnicalAssociation of the Pulp and Paper Industry (JAPAN TAPPI) also employsthis method. This test method is described in detail in Standard No. 51“Paper and Paperboard—Liquid Absorbency Test Method—Bristow Method” in“JAPAN TAPPI Paper and Pulp Test Methods, 2000 Edition”.

The ink jet recording process using the ink jet recording apparatus canbe performed, for example, as follows: First, droplets of an aqueous inkcomposition (described later) are discharged onto a recording mediumheated to a temperature range of 40 to 60° C. By doing so, an image canbe formed on the recording medium. The ink jet discharging may beperformed by any known system, and, in particular, a method fordischarging droplets with vibration of a piezoelectric element(recording method using an ink jet head that forms ink droplets bymechanical deformation of an electrostrictive element) can performexcellent image recording.

Subsequently, the recording medium is heated to a temperature range of40 to 60° C. with a print heater or a drier provided to the ink jetrecording apparatus to dry the aqueous ink composition (described later)discharged on the recording medium. By this step, water and othercomponents contained in the aqueous ink composition discharged on therecording medium are promptly evaporated and scattered, and a coating isformed by the resin particles (described later) contained in the aqueousink composition. As a result, on the recording medium, a high-qualityimage that hardly has unevenness in ink density and bleeding can bequickly formed, and since the dried matter of the ink adheres on therecording medium by forming the coating of the resin particles, theimage is fixed.

The temperature range of heating a recording medium is 40° C. or higherand 60° C. or lower. When the heating temperature of a recording mediumis 40° C. or higher, evaporation and scattering of the liquid solvent inthe aqueous ink composition can be effectively accelerated. However, ifthe heating temperature of a recording medium is higher than 60° C., forexample, deformation may occur in some types of recording media, or anydefects, such as shrink of recorded images, may occur when the recordingmedium has been cooled to room temperature.

The time heating a recording medium is not particularly limited as longas the liquid solvent contained in the aqueous ink composition isevaporated and scattered and a coating of the thermoplastic resinparticles is formed, and can be appropriately determined depending on,for example, the solvent, resin particles, and printing speed.

1.2. Aqueous Ink Composition

The aqueous ink composition used in the ink jet recording processaccording to an embodiment of the invention will be described in detailbelow.

1.2.1. Solvent

The aqueous ink composition used in the ink jet recording processaccording to this embodiment contains a first solvent composed of atleast one selected from 2-pyrrolidone, 1,3-dimethyl-imidazolidinone, andN,N′-dimethylpropylene urea, a second solvent composed of at least oneselected from 1,2-hexanediol and 1,2-pentanediol, and a third solventcomposed of at least one selected from glycol diethers having a boilingpoint of 150 to 220° C.

The first solvent composed of at least one selected from 2-pyrrolidone,1,3-dimethyl-imidazolidinone, and N,N′-dimethylpropylene urea works as asatisfactory solubilizing agent or softening agent for a thermoplasticwater-soluble resin particles described below or for polyvinyl chloridebeing a base material of the recording medium.

Since the first solvent has a boiling point of 210 to 250° C. and istherefore evaporated lastly in the heating step, it is concentrated inthe residual materials of the ink on the recording medium to a highconcentration and dissolves the thermoplastic resin particles. Thedissolved thermoplastic resin accelerates formation of a coating of thesolidified material having a main component of the coloring agent on therecording medium made of polyvinyl chloride to provide an effect fortight adhesion.

In addition, part of the first solvent contained in the aqueous inkcomposition infiltrates the recording medium, swells the recordingmedium, or dissolves the recording medium to act for furtherstrengthening the adhesion between the solidified ink and the polyvinylchloride.

The content (W1) of the first solvent is 4 mass % or more and 15 mass %or less based on the total mass of the aqueous ink composition. Thecontent (W1) of the first solvent is more preferably 6 mass % or moreand 15 mass % or less based on the total mass of the aqueous inkcomposition. A content (W1) of the first solvent of 6 mass % or more canfurther firmly fix an image formed on a recording medium. On the otherhand, a content (W1) of the first solvent of 4 mass % or less maydecrease formation of a coating of the thermoplastic resin particles inthe aqueous ink composition to make solidification and fixation of animage insufficient. When the content (W1) of the first solvent is higherthan 15 mass %, part of the first solvent remaining on the surface of arecording medium is hardly evaporated and scattered, which may causeinsufficient drying of the image.

The second solvent composed of at least one selected from 1,2-hexanedioland 1,2-pentanediol is a solvent having a low surface tension that has afunction of further increasing wettability of the aqueous inkcomposition to a recording medium by the synergistic effect with thesurfactant to let the ink uniformly wet the surface of a recordingmedium. Herein, the solvent having a low surface tension refers to asolvent having a surface tension of 40 mN/m or less at room temperature.By that the ink uniformly wets the surface of a recording medium,unevenness in ink density and bleeding of the ink on the recordingmedium can be reduced.

Preferred examples of the second solvent include 1,2-alkanediols having5 to 6 carbon atoms and a boiling point of 210 to 250° C. Since thesematerials are excellent in a function of letting the ink uniformly wetthe non-absorptive plastic surface of a recording medium, bleeding ofthe formed image can be reduced. However, 1,2-alkanediols having 4 orless carbon atoms are poor in wettability of ink to plastic recordingmedia and may cause unevenness in ink density or bleeding, and1,2-alkanediols having 7 or more carbon atoms make water solubility ofthe solvent poor, which may not allow to add the solvent in an amountnecessary for ensuring wettability or may prevent storage stability ofthe ink composition.

The content (W2) of the second solvent is 3 mass % or more and 8 mass %or less based on the total mass of the aqueous ink composition. Thecontent (W2) of the second solvent is preferably 3 mass % or more and 6mass % or less based on the total mass of the aqueous ink composition.When the content (W2) of the second solvent is 6 mass % or less, animage on a recording medium can be more quickly dried. However, when thecontent (W2) of the second solvent is less than 3 mass %, wettability ofthe ink to the polyvinyl chloride recording medium is poor, and ahigh-quality image may not be given. When the content (W2) of the secondsolvent is higher than 8 mass %, the solvent is hardly evaporated andscattered, which may cause insufficient drying of the image.

The total content (W1+W2) of the first solvent and the second solvent is18 mass % or less, based on the total mass of the aqueous inkcomposition. If the total content (W1+W2) of the solvents is higher than18 mass %, the solvents are not sufficiently evaporated in the heatingstep for drying the recording medium and remain, resulting in a decreasein quick-drying property of the image.

Since the third solvent composed of at least one selected from glycoldiethers having a boiling point of 150 to 220° C. is selected so as tohave a boiling point lower than those of the first solvent and thesecond solvent and is contained in the aqueous ink composition for inkjet recording, the third solvent is evaporated at the initial stage ofthe heat step to accelerate the drying of the ink on a recording medium.A high quick-drying property of the ink can reduce the time for heatdrying and the temperature for heating and also reduce unevenness andbleeding due to aggregation of ink to improve image quality. The thirdsolvent composed of at least one selected from glycol diethers furtherhas effects of slowly dissolving or swelling the polyvinyl chloridebeing the recording medium and fixing the solidified material having amain component of the coloring agent, which is a nonvolatile componentin the ink composition, to the dissolved portion of the polyvinylchloride film being the recording medium or letting the solidifiedmaterial infiltrate gaps generated by the swelling, in the period fromthe adhesion of ink to the polyvinyl chloride film as the recordingmedium until the evaporation of the solvent.

Dissolution of polyvinyl chloride in a glycol diether can be judged bythe following method: A polyvinyl chloride sheet (Takiron plate,manufactured by Takiron Co., Ltd.) having a thickness of 1.0 mm isimmersed in a glycol diether solvent and is left to stand at roomtemperature for one hour. Then, the sheet is taken out from the solvent,washed with water, and dried, and conditions of the sheet are observed.If no change in the conditions is observed, it is judged that there isno dissolution. If whitening, cracking, softening, swelling, or leachingis observed in the sheet, the sheet is further subjected to thefollowing adhesion test: Glycol diether (0.01 g) is dropped onto therecording surface of a strip-like recording medium sheet, and anotherstrip-like recording medium sheet is placed on the sheet so that boththe recording surfaces oppose with the dropped glycol diethertherebetween. A load of 300 g is applied onto the two recording mediumsheets, and they are left to stand for 10 minutes. Then, each strip-likesheet is subjected to a tensile test at a load of 100 g in the directionshown in the test method for tensile shearing adhesive strength ofadhesives (JIS K6850) for investigating adhesiveness. The solventshowing adhesiveness can be judged to dissolve polyvinyl chloride.

Examples of the glycol diether having a polyvinyl chloride-dissolvingproperty judged by the above-mentioned method and having a boiling pointin the range of 150 to 220° C. include diethylene glycol dimethyl ether,diethylene glycol diethyl ether, diethylene glycol ethyl methyl ether,diethylene glycol butyl methyl ether, and triethylene glycol dimethylether. Among these glycol diethers, particularly preferred arediethylene glycol diethyl ether and triethylene glycol dimethyl ether,which have boiling points of 190 to 220° C.

The content (W3) of the third solvent is 4 mass % or more and 20 mass %or less based on the total mass of the aqueous ink composition. Thecontent (W3) of the third solvent is more preferably 5 mass % or moreand 15 mass % or less based on the total mass of the aqueous inkcomposition.

In the case that the content (W1) of the first solvent in the aqueousink composition is 4 mass % or more, an image formed on the recordingmedium of a polyvinyl chloride film can have satisfactory abrasionresistance by adjusting the content (W3) of the third solvent to 4 mass% or more. In the case that the content (W1) of the first solvent in theaqueous ink composition is 6 mass % or more, an image formed on therecording medium of a polyvinyl chloride film can have more satisfactoryabrasion resistance by adjusting the content (W3) of the third solventto 5 mass % or more.

In the case that the content (W2) of the second solvent in the aqueousink composition is 3 mass % or more, a satisfactory high-quality imagewith less bleeding can be formed on the recording medium of a polyvinylchloride film by adjusting the content (W3) of the third solvent to 4mass % or more.

When the content (W3) of the third solvent in the aqueous inkcomposition is less than 20 mass %, solvent odor that is generated inthe heating step of a printed matter can be sufficiently reduced, andthe polyvinyl chloride film of the recording medium is not completelydissolved. Thus, only an effect of allowing the solidified materialformed by the ink to adhere to or infiltrate the recording medium can beobtained. When the content (W3) of the third solvent in the aqueous inkcomposition is 15 mass % or less, solvent odor that is generated in theheating step can be further reduced. However, when the content (W3) ofthe third solvent in the aqueous ink composition is higher than 20 mass%, since the surface of the recording medium of polyvinyl chloride isexcessively dissolved, defects such as deformation of the recordedmatter or generation of wrinkles occur. In addition, when the content(W3) of the third solvent in the aqueous ink composition is higher than20 mass %, since the solvent volatilizes in a short time during theheating step to increase solvent odor, it is unfavorable.

1.2.2 Coloring Agent

The aqueous ink composition used in the ink jet recording processaccording to the embodiment contains a water-insoluble coloring agent.Examples of the water-insoluble coloring agent include water-insolubledyes and pigments, but pigments are preferred. Pigments are not onlyinsoluble or hardly soluble in water but also have a property of beinghardly faded by light, gas, and so on. Therefore, the recorded matterprinted by the ink composition containing a pigment is excellent in, forexample, water resistance, gas resistance, and light resistance and hassatisfactory storage stability.

The aqueous ink composition can contain any pigment that has been usedin known ink jet recording ink compositions. Examples of the pigmentinclude organic pigments and inorganic pigments that have been used inknown ink jet recording ink compositions.

Examples of the inorganic pigment that can be used include titaniumoxide, iron oxide, and carbon black produced by a known method such as acontact method, a furnace method, or a thermal method.

Examples of the organic pigment that can be used include azo pigments(e.g., azo lake, insoluble azo pigments, condensed azo pigments, andchelate azo pigments), polycyclic pigments (e.g., phthalocyaninepigments, perylene pigments, perynone pigments, anthraquinone pigments,quinacridone pigments, dioxadine pigments, thioindigo pigments,isoindolinone pigments, and quinophthalone pigments), dye chelates(e.g., basic dye-type chelates and acid dye-type chelates), nitropigments, nitroso pigments, and aniline black. Among these pigments,those having high affinity to water are preferably used.

More specifically, examples of the pigment for black ink include carbonblacks (C.I. pigment black 7) such as furnace black, lamp black,acetylene black, and channel black; metals such as copper oxide, ironoxide (C.I. pigment black 11), and titanium oxide; and organic pigmentssuch as aniline black (C.I. pigment black 1).

Preferred examples of carbon black include carbon black manufactured byMitsubishi Chemical Corporation, such as No. 2300, 900, MCF88, No. 20B,No. 33, No. 40, No. 45, No. 52, MA7, MA8, MA100, and No. 2200B; carbonblack manufactured by Degussa Co., such as Color Black FW1, FW2, FW2V,FW18, FW200, S150, 5160, and S170, Printex 35, U, V, and 140U, andSpecial Black 6, 5, 4A, 4, and 25; carbon black manufactured by ColumbiaChemical Company, such as Conductex SC and Raven 1255, 5750, 5250, 5000,3500, 1255, and 700; and carbon black manufactured by Cabot Co., such asRegal 400R, 330R, and 660R, Mogul L, Monarch 700, 800, 880, 900, 1000,1100, 1300, and 400, and Elftex 12.

Examples of pigments that can be used for color inks include C.I.pigment yellow 1 (fast yellow G), 3, 12 (disazo yellow AAA), 13, 14, 17,23, 24, 34, 35, 37, 42 (yellow iron oxide), 53, 55, 74, 81, 83 (disazoyellow HR), 95, 97, 98, 100, 101, 104, 108, 109, 110, 117, 120, 138,150, 151, 154, 155, 180, 185, and 213; C.I. pigment red 1, 2, 3, 5, 17,22 (brilliant fast scarlet), 23, 31, 38, 48:2 (permanent red 2B(Ba)),48:2 (permanent red 2B(Ca)), 48:3 (permanent red 2B(Sr)), 48:4(permanent red 2B(Mn)), 49:1, 52:2, 53:1, 57:1 (brilliant carmine 6B),60:1, 63:1, 63:2, 64:1, 81 (rhodamine 6G lake), 83, 88, 92, 101 (ironoxide red), 104, 105, 106, 108 (cadmium red), 112, 114, 122(quinacridone magenta), 123, 146, 149, 166, 168, 170, and 172; C.I.pigment violet 1 (rhodamine lake), 3, 5:1, 16, 19 (quinacridone red),23, and 38; and C.I. pigment blue 1, 2, 15 (phthalocyanine blue R),15:1, 15:2, 15:3 (phthalocyanine blue G), 15:4, 15:6 (phthalocyanineblue E), 16, 17:1, 56, 60, and 63.

The particle diameter of the pigment is not particularly limited, butthe average article diameter is preferably 25 μm or less and morepreferably 2 μm or less. By using a pigment having an average particlediameter of 25 μm or less, clogging can be prevented from occurring, andfurther sufficient discharge stability can be realized.

The content of the pigment is preferably 0.5 to 15 mass %, morepreferably 1.0 to 10.0 mass %, based on the total mass of the inkcomposition.

The above-mentioned pigment may be subjected to various methods so thatthe pigment is more easily dispersed and stably held in the aqueous inkcomposition. Examples of the method include a method of conductingdispersion using a water-soluble resin, a method of conductingdispersion using a surfactant, and a method of providing dispersionand/or dissolution ability by chemically/physically introducing ahydrophilic functional group to the pigment particle surface. Theaqueous ink composition that is used in the printing process accordingto the embodiment can be subjected to any method mentioned above or to acombination of the methods as needed. In particular, in the method wherethe pigment is dispersed in an aqueous ink by means of a water-solubleresin, adhesiveness between a recording medium and the ink compositionand/or adhesiveness among solidified materials in the ink compositionmay be advantageously increased, at the time when the aqueous inkrecorded matter has adhered to a recording medium.

Examples of the water-soluble resin that can be used for dispersing thepigment include polyvinyl alcohols, polyvinyl pyrrolidones, polyacrylicacid, acrylic acid-acrylnitrile copolymers, vinyl acetate-acrylic acidester copolymers, acrylic acid-acrylic acid ester copolymers,styrene-acrylic acid copolymers, styrene-methacrylic acid copolymers,styrene-methacrylic acid-acrylic acid ester copolymers,styrene-α-methylstyrene-acrylic acid copolymers,styrene-α-methylstyrene-acrylic acid-acrylic acid ester copolymers,styrene-maleic acid copolymers, styrene-anhydrous maleic acidcopolymers, vinyl naphthalene-acrylic acid copolymers, vinylnaphthalene-maleic acid copolymers, vinyl acetate-maleic acid estercopolymers, vinyl acetate-crotonic acid copolymers, vinylacetate-acrylic acid copolymers, and salts thereof. Among them,particularly preferred are copolymers of monomers having hydrophobicfunctional groups and monomers having hydrophilic functional groups andpolymers of monomers having both hydrophobic functional groups andhydrophilic functional groups. The form of the copolymers may be any ofrandom copolymers, block copolymers, alternating copolymers, and graftcopolymers.

The salts are, for example, salts with basic compounds such as ammonia,ethylamine, diethylamine, triethylamine, propylamine, isopropylamine,dipropylamine, butylamine, isobutylamine, diethanolamine,triethanolamine, tri-iso-propanolamine, aminomethyl propanol, andmorpholine. The addition amount of the basic compound is notparticularly limited as long as it is not lower than neutralizationequivalent of the water-soluble resin.

The molecular weight of the water-soluble resin that can be used fordispersing the pigment is preferably in the range of 1000 to 100000,more preferably in the range of 3000 to 10000, as a weight-averagemolecular weight. When the molecular weight is within this range, thecoloring agent can be stably dispersed in water, and, for example,viscosity control in the application to the aqueous ink composition iseasy. The acid number is preferably in the range of 50 to 300 and morepreferably in the range of 70 to 150. When the acid number is withinthis range, stable dispersion of the coloring agent particles in watercan be ensured, and printing using an aqueous ink composition containingthis can provide a printed matter having high water resistance.

The above-described water-soluble resin that can be used for dispersingthe pigment may be commercially available one. Specific examples thereofinclude Joncryl 67 (weight-average molecular weight: 12500, acid number:213), Joncryl 678 (weight-average molecular weight: 8500, acid number:215), Joncryl 586 (weight-average molecular weight: 4600, acid number:108), Joncryl 611 (weight-average molecular weight: 8100, acid number:53), Joncryl 680 (weight-average molecular weight: 4900, acid number:215), Joncryl 682 (weight-average molecular weight: 1700, acid number:238), Joncryl 683 (weight-average molecular weight: 8000, acid number:160), and Joncryl 690 (weight-average molecular weight: 16500, acidnumber: 240) (the mentioned above are trade names, manufactured by BASFJapan Corp.).

Examples of the surfactant that can be used for dispersing the pigmentinclude anionic surfactants such as alkanesulfonates, α-olefinsulfonates, alkylbenzene sulfonates, alkylnaphthalene sulfonates,acrylmethyl taurates, dialkyl sulfosuccinates, alkyl sulfate salts,sulfated olefin, polyoxyethylene alkyl ether sulfate salts, alkylphosphate salts, polyoxyethylene alkyl ether phosphate salts, andmonoglyceride phosphate salts; amphoteric surfactants such asalkylpyridium salts, alkyl amino acid salts, and alkyl dimethyl betaine;and nonionic surfactants such as polyoxyethylene alkyl ether,polyoxyethylene alkyl phenylether, polyoxyethylene alkyl ester,polyoxyethylene alkyl amide, glycerin alkyl ester, and sorbitane alkylester.

The amount of the water-soluble resin or the surfactant that can be usedfor dispersing the pigment is preferably 1 to 100 mass %, morepreferably 5 to 50 mass %, based on 1 mass % of the pigment. In thisrange, dispersion stability of the pigment in water can be ensured.

Examples of the method of providing dispersion and/or dissolutionability by chemically/physically introducing a hydrophilic functionalgroup to the pigment particle surface include a method of introducing ahydrophilic functional group, for example, —OM, —COOM, —CO—, —SO₃M,—SO₂NH₂, —RSO₂M, —PO₃HM, —PO₃M₂, —SO₂NHCOR, —NH₃, or —NR₃ (in theformulae, M denotes a hydrogen atoms, an alkali metal, ammonium, ororganic ammonium; and R denotes an alkyl group having 1 to 12 carbonatoms, a phenyl group optionally having a substituent, or a naphthylgroup optionally having a substituent) to the pigment. The functionalgroup is physically and/or chemically introduced onto the pigmentparticle surface by grafting directly and/or with another group.Examples of a multivalent group include alkylene groups having 1 to 12carbon atoms, phenylene groups optionally having substituents, andnaphthylene groups optionally having substituents.

The above-mentioned surface treatment is more preferably performed bytreating the pigment particle surface with a treatment agent containingsulfur so that —SO₃M and/or —RSO₂M (M is a counter ion and denotes ahydrogen ion, an alkali metal ion, an ammonium ion, or an organicammonium ion) chemically bonds to the surface, that is, the pigment isdispersed in a solvent that does not have an active proton, does nothave reactivity with sulfonic acid, and does not or hardly dissolve thepigment and is subsequently subjected to surface treatment so that —SO₃Mand/or —RSO₂M chemically bonds to the surface of the particle by meansof amidosulfuric acid or a complex of sulfur trioxide and tertiary amineand thereby that the pigment can be dispersed and/or dissolved in water.

The surface treatment for grafting the functional group or its salt tothe surface of the pigment particle directly or with the multivalentgroup can be performed by any of various known surface treatmentprocedures. Examples of the treatment include a method of hydrophilizingthe surface of commercially available oxidized carbon black by furtheroxidizing it with ozone or sodium hypochlorite solution (e.g.,JP-A-7-258578, JP-A-8-3498, JP-A-10-120958, JP-A-10-195331, and10-237349), a method of treating carbon black with 3-amino-N-alkylsubstituted pyridium bromide (e.g., JP-A-10-195360 and JP-A-10-330665),a method of introducing a sulfone group to an organic pigment particlesurface with a sulfonating agent by dispersing the organic pigment in asolvent in which the organic pigment is insoluble or hardly soluble(e.g., JP-A-8-283596, JP-A-10-110110, and JP-A-10-110111), a method ofintroducing a sulfone group or a sulfone amino group to the surface ofan organic pigment by treating the organic pigment surface by dispersingthe organic pigment in a basic solvent that forms a complex with sulfurtrioxide and adding sulfur trioxide therein (e.g., JP-A-10-110114), butthe method of producing a surface-treated pigment to be used in theinvention is not limited these methods.

One pigment particle may be grafted with one kind of functional group ora plurality of kinds of functional groups. The kind of functional groupand its amount to be grafted may be appropriately determined dependingon dispersion stability in the ink, color concentration, and the dryingproperty at the front surface of the ink jet head.

The pigment can be dispersed in water by mixing each component, that is,a pigment, water, and a water-soluble resin when the resin is used fordispersing the pigment/a pigment, water, and a surfactant when thesurfactant is used for dispersing the pigment/a pigment and water whenthe pigment is provided with surface treatment, and a water-solubleorganic solvent, a neutralizer, and other components, according to needfor each case, with a disperser that is commonly used, such as a ballmill, a sand mill, an attritor, a roll mill, an agitator mill, aHenshcel mixer, a colloid mill, an ultrasonic homogenizer, a jet mill,or an angmill. In this case, the dispersion is preferably performeduntil the particle diameter of the pigment preferably becomes 25 μm orless, more preferably 2 μm or less, as the average diameter as describedabove for ensuring dispersion stability of the pigment in water.

1.2.3. Thermoplastic Resin Particles

The aqueous ink composition that is used in the ink jet recordingprocess according to the embodiment contains water-insolublethermoplastic resin particles. The thermoplastic resin particles have afunction of solidifying the ink and firmly fixing the solidified ink ona recording medium in the step of heating the recording medium within atemperature range of 40 to 60° C. and drying the aqueous ink compositiondischarged on the recording medium. By this function, the recordedmatter recorded by the aqueous ink composition containing the resinparticles has excellent abrasion resistance on a non-ink-absorbingrecording medium.

The thermoplastic resin particles may be added to the aqueous inkcomposition so as to be completely dissolved therein or may be containedin the aqueous ink composition as dispersed particles therein, that is,in an emulsion form or a suspension form. Preferably, the resinparticles are contained in the aqueous ink composition that is used inthe ink jet recording process according to the embodiment in an emulsionform or a suspension form. Since the viscosity of the aqueous inkcomposition can be readily adjusted to an appropriate range for the inkjet recording process according to the embodiment by containing theresin particles in the emulsion form or the suspension form.

Examples of the component of the thermoplastic resin particles includehomopolymers and copolymers of acrylic acid, acrylic acid ester,methacrylic acid, methacrylic acid ester, acrylonitrile, cyanoacrylate,acrylamide, olefin, styrene, vinyl acetate, vinyl chloride, vinylalcohol, vinyl ether, vinyl pyrrolidone, vinyl pyridine, vinylcarbazole, vinyl imidazole, and vinylidene chloride; fluorine resins;and natural resins. These copolymers can be used in any of randomcopolymer, block copolymer, alternating copolymer, and graft copolymerforms. Preferred thermoplastic resin particles are formed of an acrylicresin or a styrene-acrylic acid copolymer resin.

The thermoplastic resin particles may be those obtained by a knownmethod using a known material. For example, those disclosed inJP-B-62-1426, JP-A-3-56573, JP-A-3-79678, JP-A-3-160068, andJP-A-4-18462 may be used. In addition, those commercially available canbe used, and example thereof include Microgel E-1002 and Microgel E-5002(the mentioned above are trade names, manufactured by Nippon Paint Co.,Ltd.), Boncoat 4001 and Boncoat 5454 (the mentioned above are tradenames, manufactured by Dainippon Ink & Chemicals, Inc.), SAE1014 (thementioned above is a trade name, manufactured by Nippon Zeon Co., Ltd.),Saibinol SK-200 (the mentioned above is a trade name, manufactured bySAIDEN CHEMICAL INDUSTRY CO., LTD.), Joncryl 7100, Joncryl 390, Joncryl711, Joncryl 511, Joncryl 7001, Joncryl 632, Joncryl 741, Joncryl 450,Joncryl 840, Joncryl 74J, Joncryl HRC-1645J, Joncryl 734, Joncryl 852,Joncryl 7600, Joncryl 775, Joncryl 537J, Joncryl 1535, JoncrylPDX-7630A, Joncryl 352J, Joncryl 352D, Joncryl PDX-7145, Joncryl 538J,Joncryl 7640, Joncryl 7641, Joncryl 631, Joncryl 790, Joncryl 780, andJoncryl 7610 (the mentioned above are trade names, manufactured by BASFJapan, Inc.).

1.2.4. Surfactant

The aqueous ink composition that is used in the ink jet recordingprocess according to the embodiment contains a surfactant. Thesurfactant has a function of uniformly spreading the ink not to causeunevenness in ink density and bleeding of the ink on the recordingmedium.

Preferred examples of the surfactant include silicon-based surfactants.The silicon-based surfactants are preferably polysiloxane compounds suchas polyether modified organosiloxane. In addition, those commerciallyavailable can be used, and example thereof include YK-306, BYK-307,BYK-333, BYK-341, BYK-345, BYK-346, and BYK-348 (the mentioned above aretrade names, manufactured by BYK Chemie Japan, Inc.), KF-351A, KF-352A,KF-353, KF-354L, KF-355A, KF-615A, KF-945, KF-640, KF-642, KF-643,KF-6020, X-22-4515, KF-6011, KF-6012, KF-6015, and KF-6017 (thementioned above are trade names, manufactured by Shin-Etsu ChemicalsCo., Ltd.).

1.2.5. Water

The aqueous ink composition that is used in the ink jet recordingprocess according to the embodiment contains water. The water is themain medium of the aqueous ink composition and is a component that isevaporated and scattered in the above-described drying step.

The water is preferably water from which ionic impurities are removed asmuch as possible, such as pure water, e.g., ion-exchange water,ultrafiltration water, reverse osmosis water, or distilled water, orultrapure water. Use of water that has been sterilized by UV irradiationor addition of hydrogen peroxide can prevent occurrence of molds orbacteria for a long period of time and therefore is preferred.

1.2.6. Other Components

The aqueous ink composition that is used in the ink jet recordingprocess according to the embodiment can further contain, for example, apH adjuster, an antiseptic/antifungal agent, a corrosion inhibitor, anda chelating agent.

Examples of the pH adjuster include potassium dihydrogen phosphate,disodium hydrogen phosphate, sodium hydroxide, lithium hydroxide,potassium hydroxide, ammonia, diethanolamine, triethanolamine,triisopropanolamine, potassium carbonate, sodium carbonate, and sodiumhydrogen carbonate.

Examples of the antiseptic/antifungal agent include sodium benzoate,pentachlorophenol sodium, 2-pyridinethiol-1-oxide sodium, sodiumsorbate, sodium dehydroacetate, and 1,2-dibenzoisothiazolin-3-one.Examples of commercial products include Proxel XL2 and Proxel GXL (theabove-mentioned are trade names, manufactured by Avecia Inc.) andDenicide CSA and NS-500 W (the above-mentioned are trade names,manufactured by Nagase ChemteX Corp.).

Examples of the corrosion inhibitor include benzotriazole.

Examples of the chelating agent include ethylenediaminetetraacetate andsalts thereof (e.g., disodium dihydrogen ethylenediaminetetraacetate).

1.2.7. Physical Properties

The viscosity at 20° C. of the aqueous ink composition that is used inthe ink jet recording process according to the embodiment is preferably2 mPa·s or more and 10 mPa·s or less and more preferably 3 mPa·s or moreand 6 mPa·s or less. When the aqueous ink composition has a viscosity at20° C. within this range, since an appropriate amount of droplets of theaqueous ink composition is discharged from a nozzle to further reducecurved flying and scattering of the droplets, the aqueous inkcomposition can be suitably applied to an ink jet recording apparatus.The viscosity of the aqueous ink composition can be measured with avibration viscometer VM-100AL (manufactured by Yamaichi Electric Co.,Ltd.) by maintaining the temperature of the aqueous ink composition at20°.

2. Examples

The invention will be more specifically described with reference toexamples, but is not limited thereto.

2.1. Preparation of Aqueous Ink Composition

2.1.1. Preparation of Pigment Dispersion

In this Example, an aqueous ink composition containing a water-insolublepigment as the coloring agent was used. The pigment was dispersed in awater-soluble resin in advance and was added to the aqueous inkcomposition.

The pigment dispersion was prepared as follows: First, 3.0 parts by massof a styrene-acrylic acid copolymer (weight-average molecular weight:25000, acid number: 180) serving as a water-soluble resin was added to84.4 parts by mass of ion-exchange water containing 0.6 parts by mass of30% ammonia aqueous solution (neutralizer) and was dissolved therein. Tothe resulting solution, 12 parts by mass of the following pigment wasadded, followed by dispersion treatment with zirconia beads for 10hours. Then, coarse particles and impurities such as foreign particleswere removed by centrifugal filtration using a centrifuge, and theconcentration of the pigment was adjusted to 12 mass %. The pigmentsused for producing the pigment dispersions are as follows:

C.I. pigment black 7 (used for black pigment dispersion),

C.I. pigment yellow 74 (used for yellow pigment dispersion),

C.I. pigment red 122 (used for magenta pigment dispersion), and

C.I. pigment blue 15:3 (used for cyan pigment dispersion).

2.2. Preparation of Aqueous Ink Composition and Ink Set

Aqueous ink compositions of four colors, black, yellow, magenta, andcyan, were prepared using the pigment dispersions prepared in “2.1.1.Preparation of pigment dispersion” described above so as to havematerial compositions shown in Tables 1 and 2 as one ink set, and inksets, each composed of four colors, having different compositions wereprepared for Examples 1 to 16 and Comparative Examples 1 to 9. Theaqueous ink compositions were each prepared by placing theabove-mentioned pigment dispersion and materials shown in Tables 1 and 2in a container, stirring and mixing the mixture with magnetic stirrerfor 1 hour, and removing coarse particles and impurities such as foreignparticles by filtration through a membrane filter having a pore size of5 μm. Note that the numerical values in Tables 1 and 2 all representmass % and that the amount of ion-exchange water was adjusted so thatthe total amount of each aqueous ink composition was 100 mass %.

TABLE 1 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6First solvent 2-pyrrolidone 7.0 7.0 7.0 6.0 6.0 6.0 1,3-dimethylimidazolidinone N,N′-dimethylpropylene urea Second solvent1,2-pentanediol 1,2-hexanediol 8.0 8.0 8.0 5.0 5.0 5.0 Third solventdiethylene glycol diethyl ether triethylene glycol dimethyl 5.0 15.020.0 5.0 10.0 14.0 ether Water-insoluble pigment 4.0 4.0 4.0 4.0 4.0 4.0pigment (solid content) Aqueous resin styrene-acrylic acid 1.0 1.0 1.01.0 1.0 1.0 solid copolymer (dispersion) Thermoplastic styrene-acrylicacid 3.0 3.0 3.0 3.0 3.0 3.0 resin particle copolymer solid contentSilicon-based polyether modified 0.5 0.5 0.5 0.5 0.5 0.5 surfactantsiloxane Ion-exchange Balance in an amount to adjust the total to 100water Evaluation quick drying speed of good good good excellentexcellent excellent results property drying abrasion presence goodexcellent excellent good good excellent resistance of wearing imagequality bleeding excellent excellent excellent good good excellentExample Example Example 7 Example 8 Example 9 10 11 Example 1 Firstsolvent 2-pyrrolidone 6.0 4.0 4.0 10.0 15.0 6.0 1,3-dimethylimidazolidinone N,N′-dimethylpropylene urea Second solvent1,2-pentanediol 1,2-hexanediol 5.0 3.0 8.0 8.0 3.0 3.0 Third solventdiethylene glycol diethyl ether triethylene glycol dimethyl 15.0 4.0 5.04.0 4.0 15.0 ether Water-insoluble pigment 4.0 4.0 4.0 4.0 4.0 4.0pigment (solid content) Aqueous resin styrene-acrylic acid 1.0 1.0 1.01.0 1.0 1.0 solid content copolymer (dispersion) Thermoplasticstyrene-acrylic acid 3.0 3.0 3.0 3.0 3.0 3.0 resin particle copolymersolid content Silicon-based polyether modified 0.5 0.5 0.5 0.5 0.5 0.5surfactant siloxane Ion-exchange Balance in an amount to adjust thetotal to 100 water Evaluation quick drying speed of excellent excellentgood good excellent excellent results property drying abrasion presenceexcellent good good excellent excellent excellent resistance of wearingimage quality bleeding excellent good excellent excellent good excellentExample Example Example Example Example Example 13 14 15 16 17 18 Firstsolvent 2-pyrrolidone 6.0 7.0 8.0 9.0 15.0 1,3- 4.0dimethylimidazolidinone N,N′-dimethylpropylene urea Second solvent1,2-pentanediol 1,2-hexanediol 6.0 6.0 6.0 3.0 3.0 8.0 Third solventdiethylene glycol diethyl ether triethylene glycol dimethyl 14.0 5.0 5.015.0 15.0 6.0 ether Water-insoluble pigment 4.0 4.0 4.0 4.0 4.0 4.0pigment (solid content) Aqueous resin styrene-acrylic acid 1.0 1.0 1.01.0 1.0 1.0 solid copolymer (dispersion) Thermoplastic styrene-acrylicacid 3.0 3.0 3.0 3.0 3.0 3.0 resin particle copolymer solid contentSilicon-based polyether modified 0.5 0.5 0.5 0.5 0.5 0.5 surfactantsiloxane Ion-exchange Balance in an amount to adjust the total to 100water Evaluation quick drying speed of excellent excellent excellentexcellent excellent good results property drying abrasion presenceexcellent excellent excellent excellent excellent good resistance ofwearing image quality bleeding excellent excellent excellent excellentexcellent excellent Example Example Example Example Example 19 20 21 2223 First solvent 2-pyrrolidone 8.0 4.0 1,3-dimethylimidazolidinone 4.012.0 N,N′-dimethylpropylene urea 9.0 Second solvent 1,2-pentanediol 3.01,2-hexanediol 3.0 6.0 4.0 6.0 Third solvent diethylene glycol diethylether 6.0 6.0 triethylene glycol dimethyl ether 6.0 5.0 5.0Water-insoluble pigment (solid content) 4.0 4.0 4.0 4.0 4.0 pigmentAqueous resin styrene-acrylic acid copolymer 1.0 1.0 1.0 1.0 1.0 solid(dispersion) Thermoplastic styrene-acrylic acid copolymer 3.0 3.0 3.03.0 3.0 resin particle solid content Silicon-based polyether modifiedsiloxane 0.5 0.5 0.5 0.5 0.5 surfactant Ion-exchange Balance in anamount to adjust the total to 100 water Evaluation quick drying propertyspeed of drying excellent good excellent excellent excellent resultsabrasion resistance presence good excellent excellent excellent good ofwearing image quality bleeding good excellent good excellent good

TABLE 2 Comparative Comparative Comparative Comparative ComparativeExample 1 Example 2 Example 3 Example 4 Example 5 First solvent2-pyrrolidone 8.0 3.0 4.0 16.0 16.0 1,3- dimethylimidazolidinoneN,N′-dimethylpropylene urea Second 1,2-pentanediol solvent1,2-hexanediol 9.0 3.0 3.0 2.0 5.0 Third solvent diethylene glycoldiethyl ether triethylene glycol dimethyl 4.0 4.0 3.0 4.0 5.0 etherWater- pigment 4.0 4.0 4.0 4.0 4.0 insoluble (solid content) pigmentAqueous styrene-acrylic acid 1.0 1.0 1.0 1.0 1.0 resin solid copolymer(dispersion) Thermoplastic styrene-acrylic acid 3.0 3.0 3.0 3.0 3.0resin particle copolymer solid content Silicon-based polyether modified0.5 0.5 0.5 0.5 0.5 surfactant siloxane Ion-exchange Balance in anamount to adjust the total to 100 water Evaluation quick drying speed ofpoor excellent excellent good poor results property drying abrasionpresence excellent poor poor excellent excellent resistance of wearingimage quality bleeding excellent good poor poor good ComparativeComparative Comparative Comparative Example 6 Example 7 Example 8Example 9 First solvent 2-pyrrolidone 8.0 12.0 6.0 3.01,3-dimethylimidazolidinone N,N′-dimethylpropylene urea Second solvent1,2-pentanediol 1,2-hexanediol 2.0 8.0 3.0 8.0 Third solvent diethyleneglycol diethyl ether 3.0 3.0 triethylene glycol dimethyl 20.0 4.0 etherWater-insoluble pigment 4.0 4.0 4.0 4.0 pigment (solid content) Aqueousresin styrene-acrylic acid copolymer 1.0 1.0 1.0 1.0 solid (dispersion)Thermoplastic styrene-acrylic acid copolymer 3.0 3.0 3.0 3.0 resinparticle solid content Silicon-based polyether modified siloxane 0.5 0.50.5 0.5 surfactant Ion-exchange Balance in an amount to adjust the totalto 100 water Evaluation quick drying speed of excellent poor excellentgood results property drying abrasion resistance presence of wearingexcellent excellent good poor image quality bleeding poor excellent poorpoor

In Tables 1 and 2, the surfactant used was a silicon-based surfactant,“BYK-348” (manufactured by BYK Chemie Japan, Inc.).

2.3. Evaluation Test

2.3.1. Evaluation of Quick-Drying Property

(1) Formation of Recorded Matter

An ink jet printer, PX-G930 (manufactured by Seiko Epson Corporation),was partially remodeled and was equipped with a temperature variableheater at the paper guiding portion so that a recording medium can beheated and the temperature thereof can be controlled during recording ofan image.

The cyan inks of Examples 1 to 16 and Comparative Examples 1 to 9prepared in “2.2. Preparation of aqueous ink composition and ink set”were set to the ink jet printer. As the recording medium, a polyvinylchloride plastic film, “LLSP EX113” (manufactured by Sakurai Co., Ltd.),was used, and solid patterns were recorded thereon. The solid patternimage was formed at a resolution of 720 dpi in the vertical directionand 720 dpi in the lateral direction and a duty of 50%.

The recorded matter was formed using the ink jet printer by adjustingthe heater at the paper guiding portion to warm the recording mediumduring the recording at 50° C. and leaving to stand the recording mediumimmediately after the recording in a thermostatic chamber at 50° C. for1 minute for drying.

(2) Evaluation of Recorded Matter

The recorded matter after the drying was taken out from the thermostaticchamber, and the recorded portion was touched with a finger immediatelyafter the taking out for evaluating quick-drying property of theresulting recorded matter according to the following evaluationcriteria:

excellent: there is no adhesion of ink to the finger;

good: the surface of the recorded matter is sticky, but there is noadhesion of the ink to the finger, and the stickiness is acceptable foractual use; and

poor: there is adhesion of ink to the finger.

The evaluation results are shown in Tables 1 and 2 as the quick-dryingproperty.

2.3.2. Evaluation of Abrasion Resistance

(1) Formation of Recorded Matter

The cyan inks of Examples 1 to 16 and Comparative Examples 1 to 9prepared in “2.2. Preparation of aqueous ink composition and ink set”were each set to the ink jet printer used in “2.3.1. Evaluation ofquick-drying property”. As the recording medium, a polyvinyl chlorideplastic film, “LLSP EX113” (manufactured by Sakurai Co., Ltd.) was used,and solid patterns were recorded thereon. The solid pattern images wereformed at a resolution of 720 dpi in the vertical direction and 720 dpiin the lateral direction and a duty of 60%.

The recorded matter was formed using the ink jet printer by adjustingthe heater at the paper guiding portion to warm the recording mediumduring the recording at 50° C. and leaving to stand the recording mediumimmediately after the recording in a thermostatic chamber at 50° C. for1 minute for drying.

(2) Evaluation Method of Recorded Matter

The obtained recorded matter was maintained at 20° C. for 16 hours and,then, was rubbed with an abrader having a white cotton cloth forabrasion 10 times under a load of 500 g with a Gakushin-type rubbingfastness tester AB-301S (manufactured by Tester Sangyo Co., Ltd.). Thesurface conditions of the image were visually observed and wereevaluated by the following criteria:

excellent: there is no scratch after rubbing 10 times,

good: there are scratches on the surface after rubbing 10 times, but noscratches expose the backing, and the scratches are acceptable foractual use, and

poor: there are scratches exposing the backing after rubbing 10 times.

The evaluation results are shown in Tables 1 and 2 as abrasionresistance.

2.3.3. Evaluation of Image Quality

(1) Formation of Recorded Matter

The inks of four colors, black, yellow, magenta, and cyan, of the inkset of each of Examples 1 to 16 and Comparative Examples 1 to 9 preparedin “2.2. Preparation of aqueous ink composition and ink set” were set tothe ink jet printer used in “2.3.1. Evaluation of quick-dryingproperty”. Solid patterns were each recorded on a polyvinyl chlorideplastic film, “LLSP EX113” (manufactured by Sakurai Co., Ltd.), as therecording medium. The solid pattern images were formed at a resolutionof 720 dpi in the vertical direction and 720 dpi in the lateraldirection and a duty of 100%.

The recorded matter was formed using the ink jet printer by adjustingthe heater at the paper guiding portion to warm the recording mediumduring the recording at 50° C. and leaving to stand the recording mediumimmediately after the recording in a thermostatic chamber at 50° C. for1 minute for drying.

(2) Evaluation of the Recorded Matter

The resulting recorded matter was observed for bleeding at the portionwhere each color is in contact with other colors and evaluated by thefollowing evaluation criteria:

excellent: there is no bleeding between different colors,

good: there is a slight curve in some portions where different colorsare in contact with each other, but it is not bleeding and, therefore,is not a problem for actual use, and

poor: there is bleeding between different colors.

The evaluation results are shown in Tables 1 and 2 as image quality.

The aqueous ink composition of Examples 1 to 16 shown in Table 1 wereconfirmed from the evaluation results of the quick-drying property toshow satisfactory quick drying. The evaluation results of abrasionresistance showed that the surfaces of images recorded on the recordingmedium of the polyvinyl chloride film are hardly abraded and aretherefore excellent in abrasion resistance. Furthermore, the evaluationresults of image quality showed that the images recorded on therecording medium of the polyvinyl chloride film did not have bleeding orhad merely bleeding that does not cause a problem for actual use.

In the aqueous ink compositions of Examples 12 and 16 having a content(W3) of the third solvent of 15 mass % shown in Table 1, no solvent odorwas smelled during the heating printing. On the other hand, in theaqueous ink compositions of Example 13 having a content (W3) of thethird solvent of 20 mass % shown in Table 1, slight solvent odor wassmelled during the heating printing, but it was a degree that is not aproblem for actual use.

In the aqueous ink composition of Comparative Example 1 shown in Table2, since the content (W2) of the second solvent was higher than 8 mass%, a recorded matter inferior in quick-drying property was formed.

In the aqueous ink composition of Comparative Example 2 shown in Table2, since the content (W1) of the first solvent was less than 4 mass %, arecorded matter inferior in abrasion resistance was formed.

In the aqueous ink composition of Comparative Example 3 shown in Table2, since the content (W3) of the third solvent was less than 4 mass %, arecorded matter inferior in abrasion resistance and also having muchbleeding and being thus inferior in image quality was formed.

In the aqueous ink composition of Comparative Example 4 shown in Table2, since the content (W1) of the first solvent was higher than 15 mass %and the content (W2) of the second solvent was less than 3 mass %, arecorded matter inferior in quick-drying property and also having muchbleeding and being thus inferior in image quality was formed.

In the aqueous ink composition of Comparative Example 5 shown in Table2, since the content (W1) of the first solvent was higher than 15 mass%, a recorded matter inferior in quick-drying property was formed.

In the aqueous ink composition of Comparative Example 6 shown in Table2, since the content (W2) of the second solvent was less than 3 mass %,a recorded matter haying much bleeding and being thus inferior in imagequality was formed.

In the aqueous ink composition of Comparative Example 7 shown in Table2, since the total content (W1+W2) of the first solvent and the secondsolvent was higher than 18 mass %, a recorded matter inferior inquick-drying property was formed.

In the aqueous ink composition of Comparative Example 8 shown in Table2, since the content (W3) of the third solvent was less than 4 mass %, arecorded matter having much bleeding and being thus inferior in imagequality was formed.

In the aqueous ink composition of Comparative Example 9 shown in Table2, since the content (W1) of the first solvent was less than 4 mass %and the content (W3) of the third solvent was less than 4 mass %, arecorded matter inferior in abrasion resistance and having much bleedingand being thus inferior in image quality was formed.

2.3.4. Evaluation of Heating Temperature

The inks of four colors, black, yellow, magenta, and cyan, of the inkset of Example 10 prepared in “2.2. Preparation of aqueous inkcomposition and ink set” were set to the ink jet printer used in “2.3.1.Evaluation of quick-drying property”. Solid pattern was recorded on apolyvinyl chloride plastic film, “LLSP EX113” (manufactured by SakuraiCo., Ltd.), as the recording medium. The solid pattern image was formedat a resolution of 720 dpi in the vertical direction and 720 dpi in thelateral direction and a duty of 100%.

A recorded matter was formed using the ink jet printer by adjusting theheater at the paper guiding portion to warm the recording medium duringthe recording at 40° C. and leaving to stand the recording mediumimmediately after the recording in a thermostatic chamber at 40° C. for1 minute for drying. Another recorded matter was formed using the inkjet printer by adjusting the heater at the paper guiding portion to warmthe recording medium during the recording at 60° C. and leaving to standthe recording medium immediately after the recording in a thermostaticchamber at 60° C. for 1 minute for drying.

In all the resulting recorded matters, slight curves were generated inpart of boundaries between adjacent different colors at both heatingtemperatures, as in the evaluation results of image quality of Example10 shown in Table 1, but since they are not bleeding, it was judgedthere is no problem for practical use.

Furthermore, a printed matter was formed by using the ink jet printer byadjusting the heater at the paper guiding portion to warm the recordingmedium during the recording at 35° C. and leaving to stand the recordingmedium immediately after the recording in a thermostatic chamber at 35°C. for 1 minute for drying.

In the resulting recorded matter, bleeding obviously occurred at theboundaries between adjacent different colors, unlike the evaluationresults of image quality of Example 10 shown in Table 1.

Furthermore, when the recording medium during recording was heated to70° C. adjusting the heater at the paper guiding portion using the inkjet printer, the recording medium was softened, which made it difficultto transport the recording medium not to allow normal printing.

The invention is not limited to the above-described embodiments, andvarious modifications are possible. For example, the invention includesconfigurations that are substantially the same as those described in theembodiments (for example, a configuration having the same function,method, and result, or a configuration having the same object andeffect). The invention includes configurations in which portions notessential in the configurations described in the embodiments arereplaced with other. The invention also includes configurations thatachieve the same functions and effects or achieve the same objects ofthose of the configurations described in the embodiments. In addition,the invention includes configurations in which known techniques areadded to the configurations described in the embodiments.

What is claimed is:
 1. An ink jet recording process comprising: heatinga recording medium of a polyvinyl chloride film to a temperature rangeof 40 to 60° C. and discharging droplets of an aqueous ink compositionwith an ink jet recording apparatus; and heating the recording medium toa temperature range of 40 to 60° C. to dry the aqueous ink compositiondischarged on the recording medium, wherein the aqueous ink compositioncontains: water; at least one kind of water-insoluble coloring agent;water-insoluble thermoplastic resin particles; a surfactant; a firstsolvent composed of at least one selected from 2-pyrrolidone,1,3-dimethyl-imidazolidinone, and N,N′-dimethylpropylene urea; a secondsolvent composed of at least one selected from 1,2-hexanediol and1,2-pentanediol; and a third solvent composed of at least one selectedfrom glycol diethers having a boiling point of 150 to 220° C., and thecontent (W1) of the first solvent in the aqueous ink composition is 4 to15 mass %; the content (W2) of the second solvent in the aqueous inkcomposition is 3 to 8 mass %; the total content (W1+W2) of the firstsolvent and the second solvent is 18 mass % or less; and the content(W3) of the third solvent in the aqueous ink composition is 4 to 20 mass%.
 2. The ink jet recording process according to claim 1, wherein theglycol diethers of the third solvent are at least one selected from thegroup consisting of diethylene glycol dimethyl ether, diethylene glycoldiethyl ether, diethylene glycol ethyl methyl ether, diethylene glycolbutyl methyl ether, and triethylene glycol dimethyl ether.
 3. The inkjet recording process according to claim 1, wherein the water-insolublecoloring agent is a pigment and is dispersed in the aqueous inkcomposition with a water-soluble resin.
 4. The ink jet recording processaccording to claim 1, wherein the water-insoluble thermoplastic resinparticles are made of an acrylic resin or a styrene-acrylic acidcopolymer resin.
 5. The ink jet recording process according to claim 1,wherein the surfactant is a silicon-based surfactant.
 6. The ink jetrecording process according to claim 1, wherein the treatment of heatingthe recording medium is performed with a heater or warm air.